Rotationally stabilized contact lenses

ABSTRACT

The invention provides a lens in which the lens periphery is controlled as to each of thickness differential and both the rate of change from thinner to thicker regions and the shape of the transition from thinner to thicker regions within each of the dual thin zones. The lens of the invention substantially reduces the time for the lens&#39; auto-positioning. Additionally, the lenses of the invention maintain their on-eye orientation better as compared to conventionally stabilized lenses.

FIELD OF THE INVENTION

The invention relates to contact lenses. In particular, the inventionprovides rotationally stabilized contact lenses in which autopositioningand stabilization is improved. The application is a divisional of U.S.application Ser. No. 10/644,638 filed Aug. 20, 2003 now U.S. Pat. No.6,939,005.

BACKGROUND OF THE INVENTION

It is known that correction of certain optical defects can beaccomplished by imparting non-spherical corrective characteristics toone or more surfaces of a contact lens such as cylindrical, bifocal, ormultifocal characteristics. However, the use of these lenses isproblematic in that the lens must be maintained at a specificorientation while on the eye to be effective. When the lens is firstplaced on-eye, it must automatically position, or auto-position, itselfand then maintain that position over time. However, once the lens ispositioned, it tends to rotate on the eye due to blinking as well aseyelid and tear fluid movement.

Maintenance of the on-eye orientation of a lens typically isaccomplished by altering the mechanical characteristics of the lens. Forexample, prism stabilization, including without limitation decenteringof the lens' front surface relative to the back surface, thickening ofthe inferior lens periphery, forming depressions or elevations on thelens' surface, and truncating the lens edge, has been used.

Additionally, dynamic stabilization has been used in which the lens isstabilized by the use of thin zones, or areas in which the thickness ofthe lens' periphery is reduced. Typically, the thin zones are located attwo symmetrically lying regions, one each on the superior and inferiorregions of the lens periphery. A disadvantage of dynamic stabilizationis that, when a dynamically stabilized lens is first placed on the eye,the lens may take between 10 and 20 minutes to auto-position itself.Thus, a needs exists for improved dynamic stabilization in whichauto-positioning is achieved more quickly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of the front surface of a lens of the invention.

FIG. 2 is a graphical depiction of some of the rates of change inthickness that result from application of each of Equations I and II.

FIG. 3 is a plan view of the front surface of a lens of one embodimentof the lens of the invention.

FIG. 4 is a plan view of the front surface of a lens of a secondembodiment of the lens of the invention.

FIG. 5 is a plan view of the front surface of a lens of a thirdembodiment of the lens of the invention.

FIG. 6 is a plan view of the front surface of a lens of a fourthembodiment of the lens of the invention.

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS

It is a discovery of the invention that a dynamically stabilized contactlens with improved auto-positioning may be obtained by incorporatingcertain factors relating to the lens' periphery into the lens' design.More specifically, it is a discovery of the invention that bycontrolling the lens periphery as to each of thickness differential andboth the rate of change from thinner to thicker regions and the shape ofthe transition from thinner to thicker regions within each of the dualthin zones, a substantial reduction in time for the lens'auto-positioning may be achieved as compared to conventional dynamicallystabilized lenses. Additionally, it has been discovered that thedynamically stabilized lenses of the invention maintain their on-eyeorientation better as compared to conventionally stabilized lenses.

By “auto-positioning” is meant the automatic rotation of the lens to itstarget orientation, meaning within 10 degrees of its desired on-eyeorientation, that occurs when the lens is placed on-eye. In that thelens wearer is not able to see optimally through the lens untilauto-positioning is complete, it is desirable that such positioning iscompleted as quickly as possible.

The lenses of the present invention incorporate a specific thicknessdifferential. By “thickness differential” is meant the difference inthickness between the thickest and thinnest points of the lens'periphery. Thickness at a given point on the lens is measured in termsof the distance between the front, or object side, surface and back, oreye side, surface of the lens along a direction orthogonal to the backsurface. The thickness differential of the lens periphery in the lensesof the invention is about 200 to about 400, preferably about 240 toabout 300 μm.

By “lens periphery” is meant the non-optical portion of the lens thatlies adjacent to and surrounds the optic zone. For purposes of theinvention, the lens periphery excludes the lens edge, or outermostportion of the lens relative to its geometric center. Typically, thelens edge is about 0.02 mm to about 0.2 mm in width.

FIG. 1 depicts the front, or object side, surface of a lens of theinvention. Lens 10 has an optical zone 13. The lens' periphery surroundsoptic zone 13 and is composed of four regions; two thin zones or regions11 and two thick zones or regions 12. The two thin zones 11 are shown,in which zones the thickness of the lens periphery is reduced ascompared to the remainder of the lens periphery or regions 12. The thinzones are located at the superior, or top, and inferior, or bottomportions of the lens periphery, respectively. Preferably, the superiorand inferior thin zones are symmetrical about the 90 and 270 degreepoints, respectively. Additionally shown are two thick regions 12, whichregions are the two thickest regions of the lens periphery. Theseregions lie at opposing ends of the horizontal axis, or 0–180 degreeaxis and preferably, one region is symmetrical about the 0 degree andone is symmetrical about the 180 degrees point of the lens' periphery.

Each of the thin zones can be viewed as having two points along they-axis, outermost point 14 along the outermost edge of the thin zonethat is farthest from the lens' geometric center and inner-most point 15along the innermost edge and that is nearest the lens' geometric center.As one moves along the y-axis away from the outermost edge and point 14inwardly toward the inner-most point 15, there is a continuous increasein the thickness of the thin zone. The change in the thickness as onemoves vertically along the y-axis of the thin zone toward the geometriccenter of the lens may be linear. This thickness change may berepresented by the following equation:T=f(y)  (I)wherein T is the thickness; and

-   f(y) is a function of the thickness change as one moves along the    y-axis.

Alternatively, the thickness change may be accelerated, or non-linear,and according to the equation:T=g(y)  (II)wherein T is the thickness; and

-   g(y) is a function of the thickness change as one moves along the    y-axis.

One ordinarily skilled in the art will recognize that, for each ofEquations I and II, Cartesian, or polar coordinates may be used.Additionally, it will be recognized that Equations I and II mayrepresent any of a large number of functions. A preferred function forEquation I is:

$\begin{matrix}{T = {T_{\max} - {\left( {y - y_{0}} \right)\frac{\left( {T_{\max} - T_{\min}} \right)}{\left( {y_{1} - y_{0}} \right)}}}} & ({III})\end{matrix}$wherein T_(max) is the maximum thickness at y=y₀;

-   T_(min) is the minimum thickness at y=y₁;-   y is the function variable; and-   y₀ and y₁ are points along the y axis.

An alternative preferred function for Equation I, in polar coordinates,is as follows:

$\begin{matrix}{T = {T_{\max} - {\left( {r - r_{0}} \right)\frac{\left( {T_{\max} - T_{\min}} \right)}{\left( {r_{1} - r_{0}} \right)}}}} & ({IV})\end{matrix}$wherein T_(max) is the maximum thickness at r=r₀;

-   T_(min) is the minimum thickness at r=r₁;-   r is the function variable; and-   r₀ and r₁ are points along the r axis.

A preferred function for Equation II is:

$T = {T_{\min} + {T_{d} \cdot {\cos\left\lbrack \frac{\pi \cdot \left( {y - y_{0}} \right)}{2 \cdot \left( {y_{1} - y_{0}} \right)} \right\rbrack}^{\alpha}}}$wherein T_(min) is the minimum thickness at y=y₁;

-   (T_(min)+T_(d)) is the maximum thickness at y=y₀;-   α is coefficient that controls the shape of the transition in    thickness from T_(min) to (T_(min)+T_(d)); and-   y₀ and y₁ are points along the y axis.

In FIG. 2 is a graphical depiction of the different thickness profilesresulting from application of each of Equations I and II. The y-axis ofthe graph in FIG. 2 represents the 90–270 degree axis of the lens. Thex-axis of the graph is the thickness of the lens along the lens' y-axis.The thickness profiles shown in FIG. 2 are meant only to illustrate someof the possibilities for the shapes that may be imparted to thetransition from thin to thick regions of the thin zones of the lenses ofthe invention.

By application of Equation I, one may obtain dual thin zones as depictedin FIGS. 3 and 4. FIG. 3 depicts lens 20 with thin zones 21. Each ofthin zones 21 is composed of a plurality of horizontally extendingiso-thickness lines 22, 23, 24, and 25. By “iso-thickness line” is meantthat any point along the line, the thickness is the same as at any otherpoint along the line. The thickness within the thin zone changescontinuously as one moves from one iso-thickness line to anotherincreasing in thickness as one moves inwardly from the outermost regionof the thin zone toward the innermost region of the thin zone. Thus,outermost iso-thickness line 22 is thinner than 23, which is thinnerthan 24, which is thinner than 25.

Thus in one embodiment, the invention provides a lens, comprising,consisting essentially of, and consisting of: a first and a second thickzone and a first and second thin zone within the lens periphery; athickness differential of about 200 to about 400 μm wherein each of thethin zones comprises a plurality of horizontally extending iso-thicknesslines extending from an outermost edge to an innermost edge of the thinzone, each line having a thickness that is different from each otherline and wherein in each of the thin zones, the thickness linearlyincreases from outermost line to innermost line.

In FIG. 4 is depicted an alternative embodiment for the constant rate ofchange. FIG. 4 depicts lens 30 with thin zones 31. Each of the thinzones is composed of a number of horizontally extending iso-thicknessarcs 32, 33, 34, and 35. By “iso-thickness arc” is meant an arc-shapedline wherein for any point along the arc the thickness is the same as atany other point along the arc. The thickness of outermost iso-thicknessarc 32 is less than that of 33, which is less than that of 34, which isless than that of innermost arc 35.

In another embodiment, the lens of the invention comprises, consistsessentially of, and consists of: a first and a second thick zone and afirst and second thin zone within the lens periphery; a thicknessdifferential of about 200 to about 400 μm wherein each of the thin zonescomprises a plurality of horizontally extending iso-thickness arcsextending from an outermost edge to an innermost edge of the thin zone,each arc having a thickness that is different from each other arc andwherein in each of the thin zones, the thickness linearly increases fromoutermost arc to innermost arc.

FIGS. 5 and 6 depict dual thin zones obtained by application of EquationII in which the change in thickness as one moves inwardly from theoutermost iso-thickness line is non-linear. FIG. 5 depicts lens 40 withthin zones 41. Each of the thin zones is composed of a plurality ofiso-thickness lines 42, 43, 44, 45 and 46 each of which is of adifferent thickness, with thickness increasing as one moves fromoutermost line 42 to 43 and so forth. The thickness at any point alongthe horizontal, or x-axis, of each of the lines is the same as at anyother point, the thickness changing only as one moves from line to line.In FIG. 6 is depicted an alternative embodiment for the non-linear rateof thickness change in which iso-thickness arcs, rather thaniso-thickness lines, are used.

In yet another embodiment, the invention provides a lens comprising,consisting essentially of, and consisting of: a first and a second thickzone and a first and second thin zone within the lens periphery; athickness differential of about 200 to about 400 μm wherein each of thethin zones comprises a plurality of horizontally extending iso-thicknesslines extending from an outermost edge to an innermost edge of the thinzone, each line having a thickness that is different from each otherline and wherein in each of the thin zones, the thickness non-linearlyincreases from outermost line to innermost line.

In still another embodiment, the invention provides a lens, comprising,consisting essentially of, and consisting of a first and a second thickzone and a first and second thin zone within the lens periphery; athickness differential of about 200 to about 400 μm wherein each of thethin zones comprises a plurality of horizontally extending iso-thicknessarcs extending from an outermost edge to an innermost edge of the thinzone, each arc having a thickness that is different from each other arcand wherein in each of the thin zones, the thickness non-linearlyincreases from outermost arc to innermost arc.

The invention may be used to stabilize any lens, but may find itsgreatest utility in lenses that require on-eye stabilization to provideoptical correction. Thus, the invention may find its greatest utility intoric and multifocal lenses. Additionally, the designs may be useful inlenses customized to a specific individual's corneal topography, lensesincorporating high order wave-front aberration correction, or both.Preferably, the invention is used to stabilize toric lenses or toricmultifocal lenses as, for example, disclosed in U.S. Pat. Nos.5,652,638, 5,805,260 and 6,183,082 which are incorporated herein byreference in their entireties.

Multifocal lenses include, without limitation, bifocal and progressivelenses. One type of bifocal lens provides an optic zone with annularrings alternating between near and distance optical power. By “nearoptical power” is meant the amount of refractive power required tocorrect the wearer's near vision acuity to the desired degree. By“distance optical power” is meant the amount of refractive powerrequired to correct the wearer's distance vision acuity to the desireddegree.

The annular rings may be present on the front, or object side, surface,the back, or eye side, surface, or both surfaces of the lens. In apreferred embodiment, a first and a second ophthalmic lens is provided,the first lens having a convex surface with an optic zone that providessubstantially all of the distance optical power and a concave surfacewith an optic zone of with at least two concentric, annular portions,the power of each of the at least two annular portions substantiallyequal to that of the distance optical power. The second lens provides aconvex surface having an optic zone that provides substantially all ofthe near optical power and a concave surface that provides an optic zoneof at least two concentric, annular portions, the power of each of theat least two annular portions substantially equal to that of the nearoptical power.

Alternatively, rings of intermediate power, or power between that of thenear and distance optical power may also be provided. As yet anotheralternative, the lens may provide progressive multifocal correction.Suitable bifocal, multifocal and progressive designs are described inU.S. Pat. Nos. 5,448,312, 5,485,228, 5715,031, 5,929,969, 6,179,420,6,511,178 and 6,520,638 incorporated herein by reference in theirentireties.

As yet another alternative, the lenses of the invention may incorporatecorrection for higher order ocular aberrations, corneal topographicdata, or both. Examples of such lenses are found in U.S. Pat. Nos.6,305,802 and 6,554,425 incorporated herein by reference in theirentireties.

The lenses of the invention may be made from any suitable lens formingmaterials for manufacturing ophthalmic lenses including, withoutlimitation, spectacle, contact, and intraocular lenses. Illustrativematerials for formation of soft contact lenses include, withoutlimitation silicone elastomers, silicone-containing macromers including,without limitation, those disclosed in U.S. Pat. Nos. 5,371,147,5,314,960, and 5,057,578 incorporated in their entireties herein byreference, hydrogels, silicone-containing hydrogels, and the like andcombinations thereof. More preferably, the surface is a siloxane, orcontains a siloxane functionality, including, without limitation,polydimethyl siloxane macromers, methacryloxypropyl polyalkyl siloxanes,and mixtures thereof, silicone hydrogel or a hydrogel, such as etafilconA.

A preferred contact lens material is a poly 2-hydroxyethyl methacrylatepolymers, meaning, having a peak molecular weight between about 25,000and about 80,000 and a polydispersity of less than about 1.5 to lessthan about 3.5 respectively and covalently bonded thereon, at least onecross-linkable functional group. This material is described in U.S. Ser.No. 60/363,630 incorporated herein in its entirety by reference.

Curing of the lens material may be carried out by any convenient method.For example, the material may be deposited within a mold and cured bythermal, irradiation, chemical, electromagnetic radiation curing and thelike and combinations thereof. Preferably, for contact lens embodiments,molding is carried out using ultraviolet light or using the fullspectrum of visible light. More specifically, the precise conditionssuitable for curing the lens material will depend on the materialselected and the lens to be formed. Suitable processes are disclosed inU.S. Pat. No. 5,540,410 incorporated herein in its entirety byreference.

The contact lenses of the invention may be produced by any convenientmethod. One such method uses an OPTOFORM™ lathe with a VARIFORM™attachment to produce mold inserts. The mold inserts in turn are used toform molds. Subsequently, a suitable liquid resin is placed between themolds followed by compression and curing of the resin to form the lensesof the invention. One ordinarily skilled in the art will recognize thatany number of known methods may be used to produce the lenses of theinvention.

The invention will be clarified by a consideration of the following,non-limiting examples.

EXAMPLE Example 1

Two different lenses of the invention, Lens A and Lens B were testedon-eye for auto-positioning versus ACUVUE® Brand Toric lenses. Lenses Aand B were made using Equation III For Lens A, T_(max) was 0.418 mm andT_(min) was 0.150 mm. For Lens B, T_(max) was 0.409 mm and T_(min) was0.145 mm. For ACUVUE Toric, 496 and 606 eyes were tested for 3 minuteand 20 minute testing, respectively. For Lens A, 178 and 188 eyes weretested, respectively. For Lens B, 108 eyes were used to test at bothtimes. All lenses were hydrogel lenses made from etafilcon A.

The lenses were randomly inserted into the subject eyes withoutconsideration for rotational position. Auto-positioning was measuredusing a slit lamp biomicroscope and scale. Table 1 shows the percentageof eyes that displayed auto-positioning within 0 to 10 degrees of theoptimal lens position within 3 minutes following placement of the lenson eye. Table 2 shows the percentage of eyes displaying auto-positioningwithin 0 to 10 degrees after approximately 20 minutes followingplacement on eye.

TABLE 1 Lens 0–10 Degrees ACUVUE BRAND TORIC 70% Lens A 81% Lens B 79%

TABLE 2 Lens 0–10 Degrees ACUVUE BRAND TORIC 70% Lens A 82% Lens B 81%

The results of the testing demonstrate that the speed toauto-positioning is significantly better for Lenses A and B than for theACUVUE lens.

Example 2

Two commercially available toric lenses, Cooper Vision ENCORE™ Toric andOcular Sciences Inc. BIOMEDICS™ 55 Toric were tested along with Lens Ausing an USCAN RK 726PCI eye-track monitoring device The eyes of 10subjects were tracked at continuously over a 40 minute period andanalyzed for lens placement at 17 different time points (0.5, 1, 2, 3,4, 5, 10, 15, 20, 25, 30, 35, 36, 37, 38, 39 and 40 minutes).Significantly less rotation from the 0 point for Lens A was observed ascompared to the commercial lenses. Additionally, significantly lessvariation, once the lenses were auto-positioned, was observed for Lens Aas compared to the commercial lenses. The results demonstrate that LensA maintained on-eye orientation better as compared to the conventionallenses.

1. A lens, comprising: a zone of high order aberration correction; afirst and a second thick zone and a first and second thin zone withinthe lens periphery; a thickness differential of about 200 to about 400μm wherein each of the thin zones comprises a plurality of horizontallyextending iso-thickness lines extending from an outermost edge to aninnermost edge of the thin zone, each line having a thickness that isdifferent from each other line and wherein in each of the thin zones,the thickness linearly increases from outermost line to innermost line.2. The lens of claim 1, wherein the first thin zone is symmetrical aboutthe 90 degree point on the lens periphery and the second thin zone issymmetrical about the 270 degree point on the lens periphery.
 3. Thelens of claim 2, wherein the first thick zone is symmetrical about the 0degree point on the lens periphery and the second thick zone issymmetrical about the 180 degree point on the lens periphery.
 4. A lens,comprising a zone of high order aberration correction; a first and asecond thick zone and a first and second thin zone within the lensperiphery; a thickness differential of about 290 to about 400 μm whereineach of the thin zones comprises a plurality of horizontally extendingiso-thickness arcs extending from an outermost edge to an innermost edgeof the thin zone, each arc having a thickness that is different fromeach other arc and wherein in each of the thin zones, the thicknesslinearly increases from outermost arc to innermost arc.
 5. The lens ofclaim 4, wherein the first thin zone is symmetrical about the 90 degreepoint on the lens periphery and the second thin zone is symmetricalabout the 270 degree point on the lens periphery.
 6. The lens of claim5, wherein the first thick zone is symmetrical about the 0 degree pointon the lens periphery and the second thick zone is symmetrical about the180 degree point on the lens periphery.
 7. A lens, comprising: a zone ofhigh order aberration correction; a first and a second thick zone and afirst and second thin zone within the lens periphery; a thicknessdifferential of about 200 to about 400 μm wherein each of the thin zonescomprises a plurality of horizontally extending iso-thickness linesextending from an outermost edge to an innermost edge of the thin zone,each line having a thickness that is different from each other line andwherein in each of the thin zones, the thickness non-linearly increasesfrom outermost line to innermost line.
 8. The lens of claim 7, whereinthe first thin zone is symmetrical about the 90 degree point on the lensperiphery and the second thin zone is symmetrical about the 270 degreepoint on the lens periphery.
 9. The lens of claim 8, wherein the firstthick zone is symmetrical about the 0 degree point on the lens peripheryand the second thick zone is symmetrical about the 180 degree point onthe lens periphery.
 10. A lens, comprising a zone of high orderaberration correction; a first and a second thick zone and a first andsecond thin zone within the lens periphery; a thickness differential ofabout 200 to about 400 μm wherein each of the thin zones comprises aplurality of horizontally extending iso-thickness arcs extending from anoutermost edge to an innermost edge of the thin zone, each arc having athickness that is different from each other arc and wherein in each ofthe thin zones, the thickness non-linearly increases from outermost arcto innermost arc.
 11. The lens of claim 10, wherein the first thin zoneis symmetrical about the 90 degree point on the lens periphery and thesecond thin zone is symmetrical about the 270 degree point on the lensperiphery.
 12. The lens of claim 11, wherein the first thick zone issymmetrical about the 0 degree point on the lens periphery and thesecond thick zone is symmetrical about the 180 degree point on the lensperiphery.
 13. A method for producing contact lenses comprising the stepof designing a lens comprising: a zone of high order aberrationcorrection; a first and a second thick zone and a first and second thinzone within the lens periphery; a thickness differential of about 200 toabout 400 μm wherein each of the thin zones comprises a plurality ofhorizontally extending iso-thickness lines extending from an outermostedge to an innermost edge of the thin zone, each line having a thicknessthat is different from each other line and wherein in each of the thinzones, the thickness linearly increases from outermost line to innermostline.
 14. A method for producing contact lenses comprising the step ofdesigning a lens, comprising a zone of high order aberration correctiona first and a second thick zone and a first and second thin zone withinthe lens periphery; a thickness differential of about 200 to about 400μm wherein each of the thin zones comprises a plurality of horizontallyextending iso-thickness arcs extending from an outermost edge to aninnermost edge of the thin zone, each arc having a thickness that isdifferent from each other arc and wherein in each of the thin zones, thethickness linearly increases from outermost arc to innermost arc.
 15. Amethod for producing contact lenses comprising the step of designing alens, comprising: a first and a second thick zone and a first and secondthin zone within the lens periphery; a thickness differential of about200 to about 400 μm wherein each of the thin zones comprises a pluralityof horizontally extending iso-thickness lines extending from anoutermost edge to an innermost edge of the thin zone, each line having athickness that is different from each other line and wherein in each ofthe thin zones, the thickness non-linearly increases from outermost lineto innermost line.
 16. A method for producing contact lenses comprisingthe step of designing a lens, comprising a zone of high order aberrationcorrection a first and a second thick zone and a first and second thinzone within the lens periphery; a thickness differential of about 200 toabout 400 μm wherein each of the thin zones comprises a plurality ofhorizontally extending iso-thickness arcs extending from an outermostedge to an innermost edge of the thin zone, each arc having a thicknessthat is different from each other arc and wherein in each of the thinzones, the thickness non-linearly increases from outermost arc toinnermost arc.